Method and system for multidimensional localization and for rapid magnetic resonance spectroscopic imaging

Abstract

A method and system for providing prelocalization of a volume of interest and for rapidly acquiring a data set for generating spectroscopic images. Spatial prelocalization of a volume of interest is achieved by providing a presuppression sequence before a stimulated echo (STE) sequence and a suppression sequence during the mixing time (TM) interval of the STE sequence. The presuppression sequence includes a spatial suppression sequence to selectively saturate slices that intersect the plane selected by the STE sequence in order to define a boundary for the volume of interest, and this spatial suppression sequence is substantially repeated during the TM interval of the STE sequence. Spectroscopic imaging data is acquired by an oversampled echo planar spatial-spectral imaging sequence in which the gradient reversal frequency is a integer factor of n greater than the gradient reversal frequency required to sample the spectral width.

We claim: 
     
       1. A method of acquiring magnetic resonance spectroscopic information from multiple localized regions within a volume of interest, comprising the steps of: exciting spins in said volume of interest;   applying a readout magnetic field gradient signal in a first direction, said readout magnetic field gradient signal comprising a plurality of magnetic field gradient reversals to induce a plurality of gradient echo signals corresponding to said spins, said magnetic field gradient reversals applied at an oversampling frequency which is an integer multiple greater than one of a reference frequency required to provide a desired spectral width   acquiring said plurality of gradient echo signals; and   combining said gradient echo signals to provide a spectral signal having a spectral width equal to said desired spectral width.   
     
     
       2. The method according to claim 1, further comprising the step of editing said plurality of echo signals into sets according to whether said echo signal is associated with a positive magnetic field gradient or a negative magnetic field gradient. 
     
     
       3. The method according to claim 1, further comprising the step of processing said plurality of echo signals into a spectroscopic image comprising a spectrum for each region of said multiple localized regions. 
     
     
       4. The method according to claim 1, further comprising the step of performing phase encoding in at least one direction orthogonal to said first direction. 
     
     
       5. The method according to claim 4, wherein said step of performing phase encoding includes the step of applying a phase encoding magnetic field signal including a plurality of phase encoding magnetic field gradient pulses, and having successive one's of said plurality of phase encoding magnetic field gradient pulses applied during non-successive gradient reversal intervals.   
     
     
       6. The method according to claim 5, further comprising the step of processing said plurality of echo signals into an image. 
     
     
       7. The method according to claim 5, further comprising the step of applying a second phase encoding gradient in a third direction. 
     
     
       8. The method according to claim 1, wherein the magnitude of said readout magnetic gradient field signal is increased by said integer multiple compared to the magnitude which would be applied at said reference frequency, in order to provide a substantially equal spatial resolution. 
     
     
       9. The method according to claim 1, further comprising the steps of: applying a second readout magnetic field gradient signal in a second direction, said second readout magnetic field gradient signal comprising a plurality of second magnetic field gradient reversals to induce a plurality of second echo signals corresponding to said spins, said second magnetic field gradient reversals applied at an integer multiple of the reference frequency required to provide said desired spectral width, said second readout magnetic field gradient signal applied during an interval between successive said magnetic field gradient reversals; and   acquiring said plurality of second echo signals.   
     
     
       10. A magnetic resonance system for acquiring spectroscopic information from multiple localized regions within a volume of interest, said system comprising: means for exciting spins in said volume of interest;   means for applying a readout magnetic field gradient signal in a first direction, said readout magnetic field gradient signal comprising a plurality of magnetic field gradient reversals to induce a plurality of gradient echo signals corresponding to said spins, said magnetic field gradient reversals applied at an oversampling frequency which is an integer multiple greater than one of a reference frequency required to provide a desired spectral width   means for acquiring said plurality of echo signals; and   means for combining said gradient echo signals to provide a spectral signal having a spectral width equal to said desired spectral width.